PHP MySQL：如何选择多个表并以良好的性能返回输出摘要？

Question

如何在 PHP 上获取结果：

• NU61 - sun - 2011
• KE2I - ball - 2000
• B8WO - point - 2008

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table_first SELECT id, order, date FROM table_first ORDER BY订单 DESC return id, date

 id   | orders  | date
------+---------+------
 KE2I | 2       | 2000
 B8WO | 5       | 2008
 NU61 | 1       | 2011

table_second SELECT key FROM table_second WHERE id=(id from table_first) get key 访问 table_third 中的 content

 id   | key
------+-----------------
 KE2I | .b
 B8WO | .p
 NU61 | .s

table_third SELECT content FROM table_third WHERE id=(key from table_second)返回内容

 id   | content
------+-----------------
 .b   | ball
 .p   | point
 .s   | sun

Answer 1

SELECT `table_first`.`id`,
       `table_third`.`content`,
       `table_first`.`date`
FROM `table_first`
LEFT JOIN `table_second` USING(`id`)
LEFT JOIN `table_third` ON `table_third`.`id`=`table_second`.`key`

只要您有以下方面的索引，性能就不会成为问题：

`table_first`.`id`
`table_second`.`id`
`table_second`.`key`
`table_third`.`id`

Answer 2

这个查询可以解决问题：

SELECT t1.id, t3.content, t1.`date`
FROM table_first t1 
  JOIN table_second t2 ON t1.id = t2.id
  JOIN table_third t3 ON t2.`key` = t3.id;